Walking aid apparatus

ABSTRACT

A walking aid apparatus including a movable body and a support unit provided to the movable body to support a user further includes means for reducing a change rate of speed of the movable body with respect to a change in a force applied from the user to the support unit. With this arrangement, even when the user stumbles and applies a strong force to the support unit, the movable body can be prevented from moving suddenly, minimizing the possibility of the user being left behind the movable body.

FIELD OF THE INVENTION

The present invention relates to a walking aid apparatus which comprisesa movable body for enabling the apparatus to move and a support unit forsupporting a user to aid the user in walking.

BACKGROUND ART

As an apparatus for aiding old people and handicapped people with animpaired walking ability, there is a walking aid apparatus described inJP-A-2-5953, for example. JP-A-2-5953 discloses a walking aid apparatuswhich comprises a lower frame having a treading space for a user formedon the rear side, universal casters with braking mechanisms attached tothe front and rear parts of both left and right sides of the lowerframe, and an operation unit for operating the braking mechanisms. Asthe braking mechanism, JP-A-2-5953 discloses a brake in which when alever of the operation unit is gripped with one hand, a drive piecearranged near the caster is pivoted about a pivot shaft to abut againstthe upper end of an actuating rod, pushing down the actuating rod, whichin turn presses a braking piece, which has a friction surface forcontact with a wheel, against the wheel to render the turning andtraveling of the wheel impossible.

JP-A-5-329186 discloses a walking aid apparatus which comprises amovable body for aiding a user to walk, a support unit for supportingthe weight of the user, and a detector for detecting a force acting in adirection in which the user is walking, wherein a detected value fromthe detector is compared with its target value to control the movementof the movable body. JP-A-5-329186 also discloses control means whichcomprises left and right setters for setting target force values, leftand right comparators for comparing the target force values and thedetected force values from the force detector, scale multipliers foramplifying differential values from these comparators; and adders foradding the amplified differential values from the scale multipliers andthe target force values from the setters. JP-A-5-329186 describes thatthe use of this control means allows the user to push the walking aidapparatus with a constant force at all times regardless of the mass ofthe apparatus and an inclination of a road.

The walking aid apparatus described in JP-A-2-5953 is the one which ispushed only by the user himself. In such a push-type walking aidapparatus, when the user stumbles, he is likely to strongly push theapparatus forward and may be left behind.

In this case, although it is possible that the user may grip the leveron the operation unit to brake the apparatus by the manual brakingmechanism, it may be difficult for the user, who is old or handicapped,to operate the brake. When the user stumbles or the apparatus is used ona slope, he or she may not be able to apply brake quick enough. Thistype of apparatus therefore demands improvement in terms of operability.

While some resistance may be applied to the wheels at all times to makethe aid apparatus difficult to move and thereby eliminate thepossibility of the user getting left behind, the user needs to push theapparatus with a stronger force at all times, which obviously makes theapparatus difficult to handle.

In a walking aid apparatus which performs the movement control based onthe force applied to the apparatus from the user, like the one describedin JP-A-5-329186, when the user stumbles and applies a strong push tothe apparatus, the movement of the apparatus is controlled so that theapparatus moves greatly according to the strong force appliedinadvertently by the user, with the result that the user may get leftbehind.

Further, in this walking aid apparatus, the user can push the apparatuson a horizontal or sloped surface with a desired constant force Uref bysetting that force in the apparatus. When the force Uref set in thewalking aid apparatus is set at “0”, it is possible to stop the walkingaid apparatus even when the force applied to the apparatus on the slopedsurface is rendered “0”, i.e., the user releases his hand from theapparatus.

However, the user may lean on the apparatus to reduce the burden on hislegs or to keep his balance. In that case, the apparatus is applied witha force acting vertically and downwardly. If such a force is applied tothe apparatus on the sloped surface, the force detector detects a forcewhich is equivalent to one that tends to push the apparatus downwardlyalong the sloped surface. Hence, the apparatus is controlled to movedown the sloped surface, so that the user may be left behind.

What is described above also applies to the case where the user iswalking. When the user walks leaning on the apparatus, a verticallydownward force acts on the apparatus which is then controlled to movedown based on a force which is larger in magnitude than the userrecognizes, so that the user may be left behind.

DISCLOSURE OF THE INVENTION

The conventional apparatuses, however, do not consider automaticapplication of brake regardless of the operation on the part of the userin the above-mentioned case. It is therefore an object of the presentinvention to provide a safe walking aid apparatus which prevents such aphenomenon that the apparatus moves or is performed the movement controlwith a force applied inadvertently to the apparatus by the user and thusthe user is left behind.

To achieve the above object, a walking aid apparatus according to thepresent invention comprises a movable body and a support unit providedto the movable body, and further comprises means for reducing a changerate of a speed of the movable body with respect to a change in forceacting on the support unit when the speed of the movable body increases.

A walking aid apparatus of the present invention comprises a movablebody, a support unit provided to the movable body, and a controller forcontrolling movement of the movable body, and further comprises forcedetection means for detecting a force acting on the support unit, andcontrol means for reducing, based on a detection result in the forcedetection means, a change rate of a speed of the movable body withrespect to a change in force acting on the support unit when the speedof the movable body increases.

A walking aid apparatus of the present invention comprises a movablebody and a support unit provided to the movable body, and furthercomprises resistance application means for increasing a resistanceapplied to the movable body when a speed of the movable body increases.

In these walking aid apparatus, it is more difficult to increase thespeed of the apparatus when the moving speed is high than when themoving speed is low. Hence, even when the user stumbles and applies astrong force to the support unit, the movable body can be prevented frommoving suddenly, thus minimizing the possibility of the user gettingleft behind the apparatus. When the apparatus is moving at slow speed,it can be moved easily with a small force, thus facilitating thehandling.

Further, a walking aid apparatus of the present invention comprises amovable body, a support unit provided to the movable body, and acontroller for controlling movement of the movable body, and furthercomprises control means for detecting a force acting on the support unitto control a change rate of an acceleration with respect to a change inthe force, wherein the control means is adapted to make the change rateduring acceleration smaller than that during the deceleration.

A walking aid apparatus of the present invention comprises a movablebody, a support unit provided to the movable body, and a controller forcontrolling movement of the movable body based on a force applied to themovable body, wherein an absolute value of an acceleration when a forceis applied in a direction in which the movable body is accelerated ismade smaller than an absolute value of an acceleration when the sameforce is applied in a direction in which the movable body isdecelerated.

In these walking aid apparatus, although the acceleration performance isset low to forestall a situation where the movable body is suddenlymoved forward leaving the user behind, a high deceleration performancecan be obtained. Therefore, even when the user stops suddenly for somereason, the apparatus can be stopped quickly, thus preventing the userfrom being left behind.

Furthermore, a walking aid apparatus of the present invention comprisesa movable body, a support unit provided to the movable body, and acontroller for controlling movement of the movable body based on a forceapplied to the movable body, and further comprises inclination angledetection means for detecting an inclination angle of the movable body,wherein a movement control of the movable body is corrected based on anoutput of the inclination angle detection means so as to eliminate aninfluence of a vertical component of a force applied to the movablebody.

A walking aid apparatus of the present invention comprises a movablebody, a support unit provided to the movable body, and a controller forcontrolling movement of the movable body based on a force applied to themovable body, wherein a movement control is performed so that even whena vertical force is applied to the movable body on a slope with nohorizontal force applied, the movable body remains at its position.

On a slope, the longitudinal force components are produced by thevertical force applied to the movable body from the user, so that themovement control of the movable body is performed based on thelongitudinal force components. Generally, the vertical force applied tothe movable body from the user is not intended to move the apparatus.Thus, removing the influences of this component of force from themovement control of the movable body makes it possible to preventunwanted movement of the movable body, thereby forestalling a situationwhere the user may get left behind the apparatus.

In the above apparatus, the force applied to the movable body from theuser should be detected preferably by detecting with force detectionmeans a force applied to the support unit from the user.

Furthermore, a walking aid apparatus of the present invention comprisesa movable body, a support unit provided to the movable body, and acontroller for controlling movement of the movable body, and furthercomprises means for stopping the movable body when the means detectsthat the movable body moves back and comes within a predetermineddistance to an object.

In this walking aid apparatus, even when the user applies a backwardforce to the support unit unconsciously, the movable body can be stoppedmoving back before reaching the user.

As described above, the present invention can forestall a situationwhere the user may be left behind the walking aid apparatus.

In the foregoing description, the speed increase of the movable bodymeans to increase the speed of the movable body either in the forward orbackward direction.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view and a top view showing the construction of oneembodiment of a walking aid apparatus according to the presentinvention.

FIG. 2 is a block diagram showing the configuration of one embodiment ofa controller according to the present invention.

FIG. 3 is a block diagram showing the configuration of one embodiment ofa control system according to the present invention.

FIG. 4 is a block diagram showing the inner configuration of oneembodiment of a speed control unit according to the present invention.

FIG. 5 is a graph showing an example relationship between an operationforce and a speed of a walking aid apparatus according to the presentinvention.

FIG. 6 is a block diagram showing the inner configuration of oneembodiment of an acceleration control unit according to the presentinvention.

FIG. 7 is a graph showing an example relationship between an operationforce and an acceleration of walking aid apparatus according to thepresent invention.

FIG. 8 is a block diagram showing an example of the characteristic of awalking aid apparatus according to the present invention.

BEST MODE FOR IMPLEMENTING THE INVENTION

In the event that a user stumbles, the conventional walking aidapparatus follows a sequence of events described below, leaving behindthe user and, in the worst case, resulting in the user falling down.

(1) The user loses his or her balance for some reason or other such asstumbling.

(2) Upon stumbling, the user strongly pushes the walking aid-apparatusforward or leans on the apparatus to prevent himself from falling.

(3) The walking aid apparatus receives a strong horizontal force fromthe user. As the weight of the user bears on it, the walking aidapparatus also receives a strong vertical force.

(4) The walking aid apparatus quickly accelerates with a largeacceleration.

(5) The walking aid apparatus has a large speed in a short time.

(6) The user cannot cope with the motion of the walking aid apparatus tofurther lose his balance and to fall down.

A walking aid apparatus of the present invention controls theacceleration and speed of the walking aid apparatus to limit theprogress of the above sequence of events and thereby prevent the userfrom falling down, thus assuring safe walking.

FIG. 1 shows the construction of a walking aid apparatus of the presentinvention. A walking aid apparatus 1 has a movable body 3 which ismovable by wheels 5, and a support unit 4 for supporting a user 2. Thesupport unit 4 is mounted to the movable body 3 and moves together withthe movable body 3. The wheels 5 are connected to left and right motors7 as drive means. The walking aid apparatus 1 can be moved forward orbackward or turned by operating the motors 7.

The walking aid apparatus 1 also includes a force sensor 6 as forcedetection means to detect at least longitudinal and vertical forces anda moment about a vertical axis, which are applied to the movable body 3or the apparatus from the user 2 through the support unit 4; a speedsensor 8 as speed detection means to detect the speed of the movablebody 3; and an inclination sensor 10 as inclination angle detectionmeans to detect the inclination angle of the movable body 3 in at leastthe longitudinal direction. The walking aid, apparatus 1 also includes aproximity sensor 9 as approach detection means to detect whether or notthe user 2 contacts or approaches other than the support unit 4.

The longitudinal direction of the walking aid apparatus 1 is a directionalong the plane where the walking aid apparatus 1 is placed, and thevertical direction is a direction perpendicular to this plane.

By supporting the user 2 with the support unit 4 and by controlling thespeed or torque of the motors 7 according to the outputs of the forcesensor 6, speed sensor 8, inclination sensor 10 and proximity sensor 9to control the speed V and acceleration A of the walking aid apparatus 1with a controller 11, the user 2 is prevented from falling and is aidedin walking.

FIG. 2 is a block diagram showing the configuration of the controller 11in the walking aid apparatus of the present invention. The outputs ofthe force sensor 6, speed sensor 8 and proximity sensor 9 are input to acalculation unit 51 through an input unit 53. The calculation unit 51uses programs and parameters stored in a storage unit 52 to calculatethe speed which the motors 7 should generate, and transmits a speedinstruction 56 to a motor controller 55 through an output unit 54. Indriving the wheels 5, the motor controller 55 controls the motors 7 sothat the speed of the motor detected by the speed sensor 8 coincideswith the speed instruction 56.

Actually, one pair of the motor 7 and the speed sensor 8 is provided onthe left side of the apparatus and another pair of the motor 7 and thespeed sensor 8 is provided on the right side of the apparatus. However,when the operation of the apparatus in the longitudinal direction is tobe controlled, the motors on the left and right sides are controlled inthe same way. Thus, the two motors are represented as one motor.

The parameters stored in the storage unit 52 can be set according to thewalking ability of the user by the user or caretaker operating an inputdevice 61 such as a keyboard. The user may possess a recorded medium 63such as a floppy disk and IC card, in which parameters suited for theowner are recorded, and insert it into a reader 62 to set theparameters.

FIG. 3 is a block diagram showing the operation of the controller 11 ofthe walking aid apparatus according to the present invention. Of theelements in the controller 11, those other than the motor controller 55are actually implemented by the calculation unit 51 using the programsstored in the storage unit 52.

First, the force sensor 6 detects the longitudinal and verticalcomponents of the force applied from the user 2 onto the walking aidapparatus 1.

An operation force detection unit 21 uses the output of the inclinationsensor 10, i.e., the inclination-angle of the walking aid apparatus 1 inthe longitudinal direction, to remove the longitudinal components of theforce acting in the gravity direction from the longitudinal component ofthe output of the force sensor 6 and thereby isolate a longitudinaloperation force F₁. The following control is performed based on theoperation force F₁, so that when the weight of the user 2 is applied tothe walking aid apparatus 1 on a slope, the operation force is detectedto prevent the walking aid apparatus 1 from moving.

A friction generation unit 22 generates a friction force F_(f) accordingto the speed and operation direction of the walking aid apparatus 1, andsubtracts the operation force F₁ from the friction force F_(f) todetermine an effective operation force F₂. This prevents the walking aidapparatus 1 from moving inadvertently when a small force is applied orwhen there are errors in the force sensor 6.

A speed control unit 23 determines a target value V₁ of the speed of themovable body 3 according to the effective operation force F₂. The speedcontrol unit 23 is so set that the target speed V₁ becomes moredifficult to be increased as the effective operation force F₂ increases,thus preventing the speed V of the walking aid apparatus 1 from becomingexcessively large.

An acceleration control unit 24 limits the time change rate of a speedinstruction V₂ and at the same time makes the speed instruction V₂follow the target speed V₁. Thereby, the acceleration A of the walkingaid apparatus 1 is limited. Further, by making the change rate of theacceleration A with respect to a change in the operation force F₁ duringacceleration smaller than during deceleration, the walking aid apparatus1 can be prevented from being accelerated suddenly. Also, when thewalking aid apparatus 1 is to be stopped, it can be decelerated swiftly.

A reversing limit unit 25 normally outputs the speed instruction V₂ as amotor speed instruction V₃. When the proximity sensor 9 detects that theuser 2 contacts or approaches other than the support unit 4 of thewalking aid apparatus 1 and when the speed in the reverse direction isgiven as the speed instruction V₂, the reversing limit unit 25 producesa zero output as the motor speed instruction V₃ to stop the walking aidapparatus. Thereby, the user 2 is prevented from falling due to contactwith the walking aid apparatus 1.

A motor controller 55 compares the motor speed instruction V₃ and theoutput of the speed sensor 8, and multiplies a deviation with a gainK_(p) and its integration value with a gain K_(i) to drive the motor 7so that a motor speed V₄ coincides with the instruction value V₃. As thewalking aid apparatus 1 is driven by the wheels 5 connected to themotors 7, the speed V of the walking aid apparatus 1 coincides with themotor speed V₄. As the integration of the deviations between the motorspeed instruction V₃ and the motor speed V₄ is fed back in the motorcontroller 55, the walking aid apparatus 1 operates according to themotor speed instruction V₃ without any accumulated errors. For example,even when the walking aid apparatus 1 is placed on a slope and appliedwith a force, with which the walking aid apparatus 1 moves, due togravity, the setting of the motor speed instruction V₃ to “0” generatesa torque that cancels the effect of gravity and thus stops the walkingaid apparatus 1.

The operation of the operation force detection unit 21 is explained byreferring to FIG. 1. Suppose that on a slope 32 with an inclinationangle θ, the user 2 puts a part of his weight on the support unit 4 ofthe walking aid apparatus 1 and, while receiving a standing aid forceW_(s) in the vertical upward direction, is pushing the walking aidapparatus 1 with a horizontal forward force U_(h). In this case, if themass of the user 2 is M₂, the force W_(f) in the vertical directionacting on the legs of the user 2 is given by the following equation.

W _(f) =M ₂ g−W _(s)  (1)

The burden acting on the legs of the user 2 decreases as the standingaid force W_(s) increases.

The support unit 4 is applied with a horizontal forward force U_(h) fromthe user 2 and with a reactionary force W_(s) of the standing aid forcein the vertical downward direction. On the other hand, as the forcesensor 6 for detecting the force acting on the support unit 4 is mountedon the walking aid apparatus 1, it detects the components along x- andy-axis of a coordinate system 33 fixed to the walking aid apparatus 1.The x-axis is parallel to the slope 32 and the y-axis is parallel to adirection perpendicular to the slope 32. Hence, the forward force U_(h)and the standing aid reactionary force W_(s) are detected incombination. That is, if the components of the detected value are F_(x)and F_(y), then they are represented by the following equations.

F _(x) =U _(h)·cos θ−W _(s)·sin θ  (2)

F _(y) =−U _(h)·sin θ−W _(s)·cos θ  (3)

Here, it is assumed that the speed of the walking aid apparatus 1 iscontrolled using the detection value F_(x) in the longitudinal directionof the walking aid apparatus 1 detected by the force sensor 6.

In the case of θ>0, i.e., up slope: When the user 2 puts a part of hisweight on the walking aid apparatus 1 and receives the standing aidforce W_(s), then a negative value of −W_(s)·sin θ is added to F_(x).This produces the same effect as pulling the walking aid apparatus 1backward, so that the walking aid apparatus 1 will move backward evenwhen no forward force U_(h) is applied. Further, as the user pushes theapparatus up the slope, a large forward force U_(h) is necessary.

In the case of θ<0, i.e., down slope: The same effect is produced aspushing the walking aid apparatus 1 forward, so that the walking aidapparatus 1 moves forward even when no forward force U_(h) is applied.When the apparatus moves forward down the slope, it is necessary toapply a backward force to prevent the speed from becoming excessive.When the user 2 loses his balance and heavily leans on the walking aidapparatus 1, the apparatus may suddenly move forward to leave the user 2behind. In the worse case, the user 2 may fall down.

In the walking aid apparatus of the present embodiment, the inclinationangle θ is detected by the inclination sensor 10 and the followingcalculations are performed on the outputs F_(x) and F_(y) of the forcesensor 6 by the operation force detector 21 to eliminate the verticalcomponent and isolate and determine only the horizontal component. Thiseliminates the influences of the standing aid reactionary force W_(s)and thereby solves the problem described above.

In the coordinate system 33 fixed to the walking aid apparatus 1, theoperation force detection unit 21 calculates the components G_(x) andG_(y) of a unit vector 34 acting in the direction of gravity accordingto the following equations based on the inclination angle θ detected bythe inclination sensor 10.

G _(x)=−sin θ  (4)

G _(y)=−cos θ  (5)

Next, from the following equations using G_(x) and G_(y), the componentsU_(x) and U_(y) of the horizontal forward force U_(h) in the coordinatesystem 33 are determined by removing the components parallel to G_(x)and G_(y) from the detection values F_(x) and F_(y) of the force sensor.

U _(x) =F _(x)−(F _(x) ·G _(x) +F _(y) ·G _(y))G _(x)  (6)

U _(y) =F _(y)−(F _(x) ·G _(x) +F _(y) ·G _(y))G _(y)  (7)

Substituting the components of F_(x) and F_(y) into the above equationsresults in the following equations.

U _(x) =U _(h)·cos θ  (8)

U _(y) =−U _(h)·sin θ  (9)

It can be confirmed that the influence of the standing aid force W_(s)is eliminated to detect only the component of the forward force U_(h).

By the above calculation, the operation force detection unit 21 extractsand detects the forward force U_(h) and outputs the longitudinalcomponent U_(x) for the walking aid apparatus 1 as the operation forceF₁. As the walking aid apparatus 1 is controlled according to theoperation force F₁, the operation of the walking aid apparatus 1 is notaffected even when the user 2 leans on the walking aid apparatus 1 onthe slope.

For example, when the user 2 puts a part of his weight on the walkingaid apparatus 1 and receives the standing aid force W_(s) withoutapplying the forward force U_(h), F₁ becomes “0”. As a result, the motorspeed instruction V₃ becomes “0”, so that the walking aid apparatus 1does not move. At this time, as the walking aid apparatus 1 receives thestanding aid reactionary force W_(s) acting in the vertical downwarddirection and the gravity-acting on the mass of the walking aidapparatus 1, a force is acting on the apparatus to move it down theslope. However, the motor controller 55 generates a torque that cancelsthe external force, thus keeping the walking aid apparatus 1 at rest.

When the user 2 walks up or down the slope while putting a part of hisweight on the walking aid apparatus 1, he can walk easily without beinginfluenced by that portion of his weight carried by the apparatus.Further, even when the user loses his balance while walking on a downslope and heavily leans on the walking aid apparatus 1, the walking aidapparatus 1 is not influenced by the vertical component of the force, sothat the movement of the walking aid apparatus 1 is restricted. As aresult, the fear that the user may be left behind the walking aidapparatus 1 is eliminated, and also the risk of his falling is reduced.

The friction generation unit 22 generates a friction force F_(f) basedon the operation force F₁ and the motor speed instruction V₃. When thewalking aid apparatus 1 is at rest, the friction generation unit 22generates a static friction as the friction force F_(f). That is, whenthe operation force F₁ is equal to or less than a friction setting valueF_(f0), F_(f) and F₁ are balanced. When F₁ is in excess of F_(f0), themagnitude of F_(f) is limited to F_(f0). When the walking aid apparatus1 is in motion, the magnitude of F_(f) is set to F_(f0) and its sign isdetermined so as to hinder any speed increase.

As the speed V of the walking aid apparatus 1 is controlled by the motorspeed instruction V₃, the speed and operation direction of the walkingaid apparatus 1 can be judged from the magnitude and sign of the motorspeed instruction V₃. That is, when the magnitude of the motor speedinstruction V₃ is equal to or less than a sufficiently small valueV_(min), the walking aid apparatus 1 can be regarded as beingstationary. When V₃ is a positive value larger than V_(min), the walkingaid apparatus 1 can be decided as moving forward. When V₃ is a negativevalue smaller than −V_(min), the walking aid apparatus 1 can be regardedas moving backward. Here, V_(min) is a small value such that the user 2feels as if the walking aid apparatus 1 is at rest, and shouldpreferably be set equal to or less than 1 cm/s.

What is described above may be expressed by the following equations.

F _(f) =F ₁(when |V ₃ |≦V _(min) , |F ₁ |≦F _(f0))  (10)

F _(f) =F _(f0)(when |V ₃ |≦V _(min) , F ₁ >F _(f0))  (11)

F _(f) =−F _(f0)(when |V ₃ |≦V _(min) , F ₁ <−F _(f0))  (12)

F _(f) =F _(f0)(when V ₃ >V _(min))  (13)

F _(f) =−F _(f0)(when V ₃ <−V _(min))  (14)

The effective operation force F₂ is determined by subtracting thefriction force F_(f) from the operation force F₁ and the speed of thewalking aid apparatus 1 is controlled according to F₂, so that the user2 feels as if the friction force F_(f) is acting on the walking aidapparatus 1. This prevents the walking aid apparatus 1 from movinginadvertently when the user 2 unintentionally applies a slight force tothe walking aid apparatus 1 or when there are some errors in the forcesensor 6. The friction setting value F_(f0) will become a burden for theuser 2 when it is set at an excessively large value. Thus, the valueshould be desirably set to a small value in a range that can preventinadvertent movement. The value is preferably set to 0.5 N or less.

FIG. 4 is a block diagram showing the inner configuration of the speedcontrol unit 23. The speed control unit 23 determines a target speed bymultiplying the effective operation force F₂ by a gain K_(fv) and thenlimits it to a range from −V_(max2) to V_(max2) before outputting it asthe target speed V₁. This operation is expressed by equations asfollows.

V ₁ =K _(fv) ·F ₂(when −V _(max2) ≦K _(fv) ·F _(F2) ≦V _(max1))  (15)

V ₁ =V _(max1)(when K _(fv) ·F ₂ >V _(max1))  (16)

V ₁ =−V _(max2)(when K _(fv) F ₂ <−V _(max2))  (17)

The speed V of the walking aid apparatus 1 is controlled according tothe target speed V₁. The relation between the operation force F₁ and thetarget speed V₁, i.e., the relation between the operation force F₁ andthe speed V, when the speed V coincides with the target speed V₁ isrepresented by the solid line in the graph of FIG. 5. As the frictionforce F_(f) is acting, the speed V is kept at “0” when the absolutevalue of the operation force F₁ is equal to or less than the frictionsetting value F_(f0). When the user 2 applies a forward force to thewalking aid apparatus 1 to generate a positive operation force F₁ and F₁exceeds F_(f0), the speed V increases according to the operation forceF₁. However, when the speed reaches the speed limit value V_(max1), thespeed stops increasing. Therefore, even if a strong force is applied tothe walking aid apparatus 1 as when the user 2 stumbles, the speed V isprevented from becoming excessively large.

Further, when the user 2 applies a backward force to the walking aidapparatus 1 to generate a negative operation force F₁, the speed V issimilarly limited to −V_(max2). This prevents the user 2 from fallingbackward.

The speed limit values V_(max1) and V_(max2) can be set according to thewalking ability of the user 2. Considering the fact that the backwardwalking is more difficult than the forward walking and produces agreater risk of the user falling down, V_(max2) may be set smaller thanV_(max1). Preferably, V_(max1) should be set at 1 m/s or less andV_(max2) at 0.5 m/s or less.

The maximum values such as V_(max1) and V_(max2) may not necessarily bedetermined, and there may be cases where the object can be accomplishedby suppressing the speed increase with respect to an increase in force.

While in the example of FIG. 5 the relation between the operation forceF₁ and the target speed V₁ is represented by a solid bent line, it ispossible to set the relation so that it can be represented by a smoothcurve of a dashed line. In this case, in order to produce the fallprevention effect described above, the change rate of the speed withrespect to the change in force needs to decrease as the absolute valueof F₁ increases. That is, the inclination of the line is reduced as theabsolute value of F₁ increases. The target speed V₁ can be determinedbased on F₁ using a smooth function that satisfies the above conditions.For example, V₁ may be made proportional to the cubic root of F₁.Further, a number table may be stored in the storage unit 52 andreferenced to determine the V₁ based on F₁.

With this arrangement, as the operation force F₁ increases, the changerate of the speed with respect to the change in force decreasescontinuously, so that the speed of the apparatus can be limited toenhance safety without making the user 2 feel incongruous. On the otherhand, when the normal walking is maintained with a small force, thespeed V of the apparatus changes sufficiently greatly according to theoperation force F₁, so that the user 2 can walk easily without receivinga large resistance.

FIG. 6 is a block diagram showing the internal configuration of theacceleration control unit 24. The acceleration control unit 24 limitsthe time change rate of the speed instruction V₂ and at the same timemakes the speed instruction V₂ follow the target speed V₁. Thereby, theacceleration of the walking aid apparatus 1 is limited.

An acceleration instruction Al is determined by determining a deviationV_(d) between the target speed V₁ and the speed instruction V₂,multiplying V_(d) by a gain K_(va1), and limiting the resultant value sothat its absolute value does not exceed an acceleration limit valueA_(max1). Further, an acceleration instruction A₂ is determined bymultiplying V_(d) by a gain K_(va2) and limiting the resultant value sothat its absolute value does not exceed an acceleration limit valueA_(max2).

An acceleration/deceleration decision unit 42 compares the signs of thespeed deviation V_(d) and speed instruction V₂. When they have the samesigns, i.e., when the absolute value of the speed instruction V₂ is tobe increased, a mode selection unit 45 selects the accelerationinstruction A₁. On the other hand, when V_(d) and V₂ have oppositesigns, i.e., when the absolute value of the speed instruction V₂ is tobe reduced, the acceleration instruction A₂ is selected. The selectedacceleration instruction A₃ is integrated by an integrator 46 to outputthe integrated value as the speed instruction V₂.

As the speed instruction V₂ is determined by integrating the deviationbetween the speed instruction V₂ and the target speed V₁, the speedinstruction V₂ follows V₁. The speed V of the walking aid apparatus 1 iscontrolled so as to coincide with the speed instruction V₂. As the speedinstruction V₂ is obtained by integrating the acceleration instructionA₃ the speed V coincides with the integration of the accelerationinstruction A₃. That is, the acceleration instruction A₃ coincides withthe acceleration A of the walking aid apparatus 1.

Although the gains K_(va1) and K_(va2) and the acceleration limit valuesA_(max1) and A_(max2) are determined according to the walking ability ofthe user 2, the parameters K_(va1) and A_(max1) for acceleration are setsmaller than the parameters K_(va2) and A_(max2) for deceleration.

FIG. 7 shows the relation between the operation force F₁ and theacceleration instruction A₃ i.e., the relation between the operationforce F₁ and the acceleration A of the walking aid apparatus 1, when thespeed instruction V₂ is a certain positive value V₂₀, i.e., the walkingaid apparatus 1 is moving forward at the speed V₂₀.

As the gain K_(va1) is set smaller than K_(va2), the inclination of thegraph changes depending on the sign of the acceleration A. The changerate of the acceleration A with respect to the change in the operationforce F₁ when the acceleration A becomes positive, i.e., the apparatusis accelerated is smaller than that when the apparatus is decelerated.

When the user 2 pushes the walking aid apparatus 1 forward, a positiveoperation force F₁ is detected. If F₁ is equal to F_(f0)+V₂₀/K_(fv), thetarget speed value V₁ becomes equal to V₂₀ by the action of the frictiongeneration unit 22 and the speed control unit 23, so that the speeddeviation V_(d) becomes “0” and the acceleration instruction A₃ becomes“0”. Hence, the walking aid apparatus 1 continues to move forward at aconstant speed of V₂₀.

When the user 2 increases the force with which he pushes the walking aidapparatus 1, the operation force F₁ is increased, so that the speeddeviation V_(d) becomes positive. As a result, the accelerationinstruction A₁ is selected, so that the acceleration instruction A₃becomes positive value K_(va1)·V_(d). Hence, the walking aid apparatus 1increases its speed with acceleration K_(va1)·V_(d). When the operationforce F₁ further increases, the acceleration A of the walking aidapparatus 1 further increases. However, the change rate of theacceleration is smaller than when the acceleration A is negative. Themagnitude of the acceleration A is limited so that it does not exceedthe acceleration limit value A_(max1).

On the other hand, when the user 2 either reduces the force with whichhe is pushing the walking aid apparatus 1 or pulls back the walking aidapparatus 1 to reduce the operation force F₁, the speed deviation V_(d)becomes negative. As a result, the acceleration instruction A₂ isselected, so that the acceleration instruction A₃ becomes k_(va2)·V_(d).Hence, the walking aid apparatus 1 decelerates due to the negativeacceleration K_(va2)·V_(d). When the operation force F₁ furtherdecreases, the acceleration A of the walking aid apparatus 1 becomes alarger negative value, but its change rate is greater than when theacceleration A is positive. The absolute value of the accelerationinstruction A₃ is limited so that it does not exceed A_(max2).

As the acceleration A of the walking aid apparatus is controlled asdescribed above, even when the user 2 stumbles and applies a strongforward force to the walking aid apparatus 1, the walking aid apparatus1 is prevented from accelerating suddenly. Thus, the possibility of theuser 2 being left behind the walking aid apparatus 1 is eliminated, andthe risk of his falling down can be reduced. On the other hand, when theuser 2 leaves the walking aid apparatus 1 and the operation force F₁becomes “0” or when the user 2 applies a backward force to stop thewalking aid apparatus 1, a sufficiently large negative acceleration isgenerated. Thus, it is possible to quickly stop the walking aidapparatus 1. Further, as the magnitude of the negative acceleration islimited by the acceleration limit value A_(max2), the user 2 can beprevented from clashing against the walking aid apparatus 1.

The acceleration limit value A_(max1) during acceleration is set at asmall value in such a range that the user 2 will not feel uncomfortablehandling the apparatus. It should preferably be set to 1 m/s or less.The acceleration limit value A_(max2) during deceleration is set so thatthe walking aid apparatus can be stopped safely and swiftly. It shouldpreferably be set in a range from 1 m/s to 5 m/s.

The characteristic of the walking aid apparatus according to the presentinvention is represented by a block diagram of FIG. 8. This diagramshows only the effects of the speed control unit 23 and the accelerationcontrol unit 24, and not the influences of the speed limit value and theacceleration limit value. The gain K_(va) is switched to K_(va1) duringacceleration and to K_(va2) during deceleration. From the block diagram,the transfer function of the pushing force F acting on the walking aidapparatus 1 and the speed V of the apparatus 1 is determined as follows.

H(s)=1/{s/(K _(fv) ·K _(va))+1/K _(fv)}  (18)

Generally, the transfer function of a system having an inertia M and aviscous resistance L is given by 1/(Ms +L). When it is compared with theabove equation, we obtain the following equation.

M=1/(K _(fv) ·K _(va)), L=1/K _(fv)  (19)

That is, by setting the gains K_(fv) and K_(va), it is possible tofreely set the apparent inertia and viscosity of the walking aidapparatus 1. The apparent inertia M changes to Ma¹ during accelerationand to Ma² during deceleration because the gain K_(va) assumes differentvalues at acceleration and at deceleration.

When the apparent viscosity L is too small, the walking aid apparatus 1moves too easily and becomes unstable. When the apparent viscosity L istoo large, the force required to push the apparatus becomes large.Hence, L should-be set at an appropriate value according to the walkingability of the user. It should preferably be set in a range of 20 Ns/mto 500 Ns/m. Therefore, the gain K_(fv) is preferably set in a range of0.002 m/sN to 0.05 m/sN.

In order to prevent sudden acceleration, the apparent inertia Ma¹ duringacceleration should preferably be set large in a range that will notmake the user 2 feel uncomfortable handing the apparatus. It should bepreferably set in a range of 50 kg to 200 kg.

The apparent inertia Ma² during deceleration should preferably be setsmaller than Ma¹ so that the apparatus can be stopped swiftly. It shouldbe preferably set to 0.6 or less times Ma¹. K_(va1) and K_(va2) are setbased on K_(fv), Ma¹ and Ma².

The attenuation time constant T for the speed V of the walking aidapparatus 1 when the user 2 leaves the walking aid apparatus 1 can beexpressed as M/L, which is 1/K_(va). In order to attenuate the speed Vswiftly, the smaller the time constant T, the better. It should bepreferably set to 2 seconds or less. Therefore, K_(va) should bepreferably set at 0.5 [1/s] or more.

The reversing limit unit 25 prevents the user 2 from falling down due tohis contact with the walking aid apparatus 1. When the walking aidapparatus 1 contacts the front part of the user while moving back, theuser will grip the support unit 4 to avoid falling. This generates thebackward operation force F₁. When the walking aid apparatus 1 movesfurther back, it is probable that the user 2 may fall. When the speedinstruction V₂ is negative, i.e., the backward speed instruction isbeing applied, and when the proximity sensor 9 detects that the user 2contacts or comes close to other than the support unit 4 of the walkingaid apparatus 1, the reversing limit unit 25 sets the motor speedinstruction V₃ to “0”, to stop the walking aid apparatus. This preventsthe falling of the user 2.

As the legs of the user 2 in particular are likely to contact thewalking aid apparatus, the proximity sensor 9 is preferably attached tothe lower inner side of the walking aid apparatus 1 to detect theapproaching legs of the user 2. The proximity sensor 9 may use, forexample, a contact type touch sensor, a beam interruption detectionsensor, an optical measuring type sensor, an ultrasonic distance sensor,and so forth.

The above embodiment describes the longitudinal motion of the walkingaid apparatus 1. However, it is possible to perform the similar controlon a rotary motion by detecting a moment about a vertical axis ratherthan the longitudinal force and by driving the left and right motors inopposite directions rather than driving them in the same directions.

In above embodiment, the motor controller 55 uses a speed control typemotor controller which compares the speed instruction 56 given by thecalculation unit 51 with the motor speed detected by the speed sensor 8and performs a speed feedback to control the motor speed. However, it ispossible to use a torque command type motor controller that controls thetorque of the motor according to the torque command. In that case, thecalculation unit 51 performs a speed feedback calculation to determinethe required torque and sends the torque command to the motorcontroller.

When the torque command type motor controller is used, it is alsopossible to calculate according to the inclination angle detected by theinclination sensor 10 a torque required to cancel the influences of thegravity acting on the walking aid apparatus 1 and the vertical forceapplied from the user 2 to the walking aid apparatus 1, and then to addit to the torque command.

With this method, the necessary torque can be produced without timedelay compared with a case where the inner integral element of the speedcontrol type motor controller generates a torque for canceling theinfluences of external forces.

In the above embodiment, the motor 7 controls the speed and accelerationof the walking aid apparatus 1. However, a controllable brake such as anelectromagnetic brake may be used instead of the motor. When the brakeis used, an aiding torque for moving up a slope cannot be provided, butit is possible to prevent with lower cost the movement of the apparatusdown the slope and excess speed.

Further, to realize an inexpensive construction, a mechanism such as abrake using a viscous fluid which produces resistance according to thespeed may be attached to the wheels 5 in order to realize the relationbetween the force and the speed as shown in FIG. 5.

What is claimed is:
 1. A walking aid apparatus which aids a user inwalking, comprising: a movable body having a support unit which supportsthe walking user for walking movement of the user; a drive which enablesmovement of the movable body; a controller which controls movement ofthe movable body by control of the drive; and a speed detector whichdetects the speed of movement of the movable body; the controllercontrolling the speed of the movable body at least in accordance with anoutput of the speed detector and reducing a change rate of the speed ofmovement of the movable body with respect to a change in force acting onthe support unit which supports the walking user for walking movementwhen the speed of movement of the movable body increases.
 2. A walkingaid apparatus according to claim 1, wherein the support unit whichsupports the walking user includes a portion engagable by hands of theuser which provide support for the walking user.
 3. A walking aidapparatus according to claim 1, further comprising a resistancegenerator which reduces the speed of movement of said movable body.
 4. Awalking aid apparatus according to claim 1, wherein an absolute value ofan increment of a velocity in acceleration of said movable body issmaller than an absolute value of a decrement of a velocity indeceleration of the movable body when the same force is applied to thesupport unit by the user in the acceleration and deceleration of themovable body.
 5. A walking aid apparatus according to claim 1, whereinthe controller controls said movable body to stay at a position thereofwhen a vertical force is applied to the movable body on a slope withouta horizontal force.
 6. A walking aid apparatus according to claim 1,further comprising a proximity sensor which detects an objectapproaching the movable body, the controller stopping movement of themovable body when the proximity sensor detects the object within apredetermined distance.
 7. A walking aid apparatus which aids a user inwaking, comprising: a movable body having a support unit which supportsthe walking user for walking movement of the user; a drive which enablesmovement of the movable body; a controller which controls movement ofthe movable body using the drive; a force detector which detects a forceacting on the support unit by the user; and a speed detector whichdetects the speed of movement of the movable body; the controllercontrolling the speed of movement of the movable body based on detectionresults of the speed detector and the force detector and decreasing achange rate of the speed of movement of the movable body with respect toa change in force acting on the support unit when the speed of movementof the movable body increases.
 8. A walking aid apparatus according toclaim 7, wherein the support unit which supports the walking userincludes a portion engagable by hands of the user which provide supportfor the walking user.
 9. A walking aid apparatus according to claim 7,further comprising a resistance generator which reduces the speed ofmovement of the movable body.
 10. A walking aid apparatus according toclaim 7, wherein the controller controls a change rate of anacceleration of the movable body with respect to a change in thedetected result of force detected by the force detector, and wherein thechange rate of the speed of the moveable body with respect to controllerdecreases the change in force acting on said support unit inacceleration of the movable body as compared with a deceleration of saidmovable body.
 11. A walking aid apparatus according to claim 7, whereinan absolute value of an increment of a velocity in acceleration of themovable body is smaller than an absolute value of a decrement of avelocity in deceleration of the movable body when the same force isapplied to the support unit by the user in the acceleration anddeceleration of the movable body.
 12. A walking aid apparatus accordingto claim 7, wherein the controller controls the movable body to stay ata position thereof when a vertical force is applied to the movable bodyon a slope without a horizontal force.
 13. A walking aid apparatusaccording to claim 7, further comprising a proximity sensor whichdetects an object approaching the movable body, the controller stoppingmovement of the movable body when the proximity sensor detects theobject within a predetermined distance.